1. Field of the Invention
This invention relates to a method of manufacturing a semiconductor device, which is applied to form a minute opening pattern (extraction pattern) having a diameter of 0.2 .mu.m or less.
2. Description of the Related Art
EB (electron beam) drawing is widely employed as a method for forming a minute opening pattern with a diameter of 0.2 .mu.m or less in an insulating layer and the like for constituting a semiconductor device. In EB drawing, to obtain a minute extraction pattern, an insulating layer and the like are patterned using, in particular, a positive resist consisting of PMMA (polymethylmethacrylate) having high resolution.
A multilayer resist process using a plurality of resist layers, or a method using an image-reversal process and a multilayer resist process are used to form a minute opening pattern. For example, SPIE (The Society of Photo-Optical Instrumentation Engineers), Vol. 773 (1987), pages 61 to 67 discloses a method using an image-reversal process and a multilayer resist process.
When an opening pattern is formed by using a high-resolution resist such as PMMA, since the quality of the resist have been improved and a thin resist film can be formed, high definition of a level of 0.1 .mu.m to 0.05 .mu.m is obtained. However, PMMA is not very much resistant to RIE (reactive ion etching) or heat. Hence, process conditions are strictly limited in the step of etching during transcription.
Moreover, since the resist consisting of PMMA and the like is not highly sensitive to light, a long period of time is required for drawing, and development conditions are also limited in detail. Hence, the throughput in manufacturing semiconductor devices by means of this method is low.
Further, the multilayer resist process requires a larger number of manufacturing steps than a single layer resist process. In addition, although the dimensions of the top resist layer can be measured, the dimensions and configuration of lower resist layers cannot be measured unless the cross section is checked. The dimensions of the opening pattern can be measured by an SEM (scanning-type electronic microscope); however, to measure the dimensions of the cross section precisely, wafers must be broken in the PMMA resist process and in the multilayer resist process.
When the dimensions of an opening pattern are measured by using an SEM without breaking wafers, definition of a level of only 0.2 .mu.m is obtainable in a conventional device, and the resist on the periphery of the opening is charged up during measurement, so that the dimensions cannot be measured.